1. Technical Field
The present invention relates to a grinding method to perform grinding while rotating a grinding wheel subjected to a dressing process.
2. Description of Related Art
In order to form a cutting edge on an outer peripheral surface of a grinding wheel, dressing (setting) of the grinding wheel is performed. In a state where a diamond dresser cuts into a depth of several tens of μm from the outer peripheral surface (operating surface) of the grinding wheel, while rotating the grinding wheel, the dressing is performed by sending the dresser at a constant speed in a direction of a rotation axis. This dressing forms a helical groove on the outer peripheral surface of the grinding wheel.
While rotating the grinding wheel which has been dressed, grinding is performed by moving a workpiece back and forth in a circumferential speed direction of the grinding wheel. When the grinding is performed in a state where the outer peripheral surface of the grinding wheel is cut to a depth of several μm to ten-odd μm from a surface of the workpiece, a helical groove formed on the outer peripheral surface of the grinding wheel is transcribed and a straight line-shaped grinding trace is formed on the surface of the workpiece. The grinding trace includes a ridge portion and a valley portion which are alternately arranged.
The grinding trace formed when the workpiece is moved forward (during forward grinding) and the grinding trace formed when the workpiece is moved backward (during backward grinding) are tilted with respect to a moving direction of the workpiece in directions opposite to each other and intersect each other. The ridge portion formed during a forward movement is cut out at an intersection point with the valley portion formed during a backward movement. In addition, the ridge portion formed when moving backward is also cut out at the intersection point with the valley portion formed when moving forward. A region where the ridge portion is disconnected and a region where the ridge portion remains periodically appear in a grinding direction. If a surface plate painted in red lead is rubbed against the surface which has been ground, a region where a high ridge portion remains is colored and a region where the ridge portion is disconnected is not colored. Accordingly, a shading pattern is observed. This shading pattern periodically appears in the grinding direction, and is called a chatter pattern.
PTL 1 discloses a grinding method which can prevent occurrence of the chatter pattern. The grinding method employs the grinding wheel subjected to the dressing process in one direction. It is possible to suppress the occurrence of the chatter pattern by rotating the grinding wheel in opposite directions during the forward movement and the backward movement of the workpiece.